Angelina Jolie and Brad Pitt have opted for fertility treatments when they decided to have more children, a source told Us Weekly.

A friend of the couple said the new parents conceived through in vitro fertilization and that they “desperately” wanted more babies soon.

Jolie turned to this very expensive procedure, the source said, because she didn’t want to “deal with the stress of trying to get pregnant.”

The chance of having fraternal twins at Jolie’s age usually is under 1 percent, but, due to in vitro, the chances rise to 25 percent.

Twins Knox Leon and Vivienne Marcheline were born on July 12 at a hospital in Nice, France, joining their siblings Maddox,6, Pax, 4, Zahara, 3, and Shiloh, 2.

The Jolie-Pitt couple have spoken several times about their desire to have several more children and said it was difficult to decide how many children they wanted. Jolie said on “The Daily Show” last year that the number fluctuated “between seven and 13 or 14.” She added that she and her partner felt they were up to challenge.

The actress also told Elle U.K. some time ago that “if we're going to have 10 kids, we'd like to raise them while we're young.”

In the meantime, Brad Pitt is also busy fighting some paparazzi that took recent photos of him, Angelina Jolie and their kids, playing in the backyard of their private French castle.

Pitt’s lawyers claim that the photos were taken by using a powerful telephoto lens and then sold to an unidentified buyer. Pitt says the pics represent a violation of his privacy rights under French and California law.

One of the agencies that sold the pictures has agreed to remove the images from its website and stop their sale.

The couple had chosen to spend the summer at Chateau Miraval, in Provence, especially because of the privacy and exclusivity that the resort offered. But it seems they could not escape the eye of the media, not even in such a secure place.